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Opposite effects of diazepam and beta-CCE on immobility and straw-climbing behavior of rats in a modified forced-swim test.

The present study was undertaken to examine how two ligands of the benzodiazepine receptor, which possess anxiolytic or anxiogenic actions, affect both the duration of immobility and the incidence of straw-climbing behavior in rats in a modified forced-swim test. Rats were injected IP with either vehicle, diazepam (0.5, 1, 5 mg/kg), or beta-carboline-3-carboxylic acid ethyl ester (beta-CCE; 0.5, 1, 2, 5 mg/kg), or a combination of diazepam at 1 mg/kg and beta-CCE at 2 mg/kg. In addition, Ro 15-1788 (1 mg/kg), a specific benzodiazepine antagonist, was injected IP 20 min after diazepam injection and immediately after beta-CCE injection, respectively. In the first 5-min period of the forced-swim test, diazepam at 5 mg/kg prolonged the duration of immobility, whereas beta-CCE at 1, 2 and 5 mg/kg reduced its duration. Immediately after the first 5-min test period, 4 straws were suspended above the surface of the water, and the number of straw-climbing attempts and the duration of immobility were measured for a subsequent 5-min test period. Straw-suspension elicited straw-climbing behavior in forced swimming rats, resulting in a shortening of the duration of immobility in this period. All doses of diazepam inhibited straw-climbing attempts and prolonged the duration of immobility in a dose-dependent manner. beta-CCE at 1 or 2 mg/kg enhanced straw-climbing attempts, but did not significantly affect the duration of immobility. Furthermore, the combined administration of diazepam and beta-CCE antagonized the respective drug effects on the duration of immobility and the number of straw-climbing attempts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Monologue speech: effects of d-amphetamine, secobarbital and diazepam.

Drugs of abuse from different pharmacological classes increase social conversation. Alcohol and d-amphetamine also increase rates of talking in subjects producing speech monologues in an isolated context. This latter finding suggests that the increases observed during dyadic social conversation may represent general increases in talking and not specific effects on social interaction. The present study was conducted to assess whether other abused drugs also increase monologue speaking. The acute effects of secobarbital (0, 50, 150, 250 mg), d-amphetamine (0, 25 mg) (Experiment 1), and diazepam (0, 10, 20, 40 mg) (Experiment 2) were investigated in healthy, adult volunteers. Secobarbital and d-amphetamine both increased the total amount of speech emitted, while diazepam generally had no effect or decreased talking. Experiment 3 was conducted to further compare the effects of secobarbital (0, 50, 150, 250 mg) and diazepam (0, 5, 15, 25 mg) using a within-subject, crossover design. Secobarbital increased talking in three of the four subjects studied, while diazepam, again, had no effect or decreased talking. In contrast to the differences noted with talking, secobarbital and diazepam both decreased response rates in a nonverbal performance task (i.e., circular-lights procedure); they also produced many similar effects on various subject-rated measures of drug effect. Thus, the differences in the effects of these two compounds on talking are not the result of a general difference in their overall profile of behavioral effects. In summary, the results obtained with secobarbital and d-amphetamine further demonstrate that an explicitly social context is not a necessary condition to observe drug-produced increases in speech quantity. The failure of diazepam to reliably increase talking in the present study illustrates the existence of some pharmacological specificity in the effect of drugs on human speech, and suggests another way in which the behavioral effects of the barbiturates and benzodiazepines may differ.

Administration, Oral↗

A comparison of the effects of diazepam and scopolamine in two positively reinforced learning tasks.

In a helical maze scopolamine (0.5 and 1 mg/kg) significantly impaired the ability of rats to acquire a spatial learning task using reference memory. In contrast, diazepam (0.5-2 mg/kg) did not impair acquisition of this task and the only effect of diazepam (4 mg/kg) was likely to be secondary to sedative effects. Diazepam (0.5-4 mg/kg) did not impair 8-day retention of the helical maze. In a test of working and reference memory in which spatial processing was minimised, scopolamine (0.5 and 1 mg/kg) significantly impaired acquisition and increased the number of reference memory errors. Diazepam (1 and 4 mg/kg) did not impair acquisition of this task, but when a delay was interposed in the middle of a trial the diazepam-treated rats were slower to complete the task than the controls and made more errors of both working and reference memory. In contrast, when the rats were tested with a change of context, the diazepam-treated rats completed the task more quickly than the controls and made fewer errors of both working and reference memory.

Animals↗

Effects of systemic and intra-amygdaloid diazepam on long-term habituation of acoustic startle in rats.

Two experiments were conducted to examine the effects of the anxiolytic drug, diazepam, on long-term habituation of the acoustic startle response. The experiments were based upon the hypothesis that manipulations that reduce fear should enhance long-term response decrements by reducing a fear-like sensitization process. In Experiment 1 rats given intraperitoneal injections of 0.5, 1.2, or 2.5 mg/kg showed larger decrements of startle amplitude than vehicle-injected controls both over trials within sessions and over days. In Experiment 2 rats injected with 35 micrograms of diazepam bilaterally into the amygdala showed larger decrements of startle amplitudes over days than vehicle-injected controls. No within-session startle effects were detected in Experiment 2. Freezing behavior was measured in Experiment 2 as an index of fear, and the amygdala injections of diazepam retarded the development of fear in the startle chamber. This index of fear was not possible in Experiment 1 because of the sedating effects of systemic diazepam. We conclude that diazepam, acting at least in part through the amygdala, attenuates the fear-like sensitization process associated with the acoustic startle stimulus. By attenuating sensitization diazepam produces larger than normal reductions in startle amplitudes over trials and days without significantly affecting initial responsiveness.

Acoustic Stimulation↗

Interaction of felbamate and diazepam against maximal electroshock seizures and chemoconvulsants in mice.

The anticonvulsant effects of felbamate alone or in combination with diazepam were investigated against maximal electroshock-, pentylenetetrazol-, isoniazid- and bicuculline-induced seizures in mice. A single subprotective dose of felbamate, a dose which offers no protection to animals when combined with diazepam, enhanced the protective effects of diazepam against seizures induced by electroshock, pentylenetetrazol and isoniazid, as measured by significant reduction of ED50 values. However, felbamate failed to significantly affect the protective action of diazepam against bicuculline. Felbamate does not interact directly with the GABA-benzodiazepine-ionophore complex. Thus the enhancement of anticonvulsant activity of diazepam by felbamate against maximal electroshock and pentylenetetrazol may involve an indirect effect at benzodiazepine receptors. The anticonvulsant action of felbamate against isoniazid does not seem to involve benzodiazepine receptors and may be due to reversing the inhibitory effect of isoniazid on glutamate decarboxylase (GAD) activity. The interaction between felbamate and diazepam may also involve other mechanisms.

Animals↗

Genetic differences in the development of physical dependence upon diazepam in Lewis and Fischer 344 inbred rat strains.

The purpose of the present study was to investigate physical dependence upon diazepam systematically in two inbred strains of rats, Lewis (LEW) and Fischer 344 (F344). Rats were chronically fed food containing diazepam on an escalating drug dosage schedule, from 1 and 2 to 12 mg/g of food, over a period of 30 days. During treatment, the growth curve in LEW and F344 rats was suppressed compared with the respective controls. Motor incoordination was evaluated by a rotarod performance test. The ranking of the motor incoordination during the final concentration of diazepam was as follows: F344 greater than LEW. After substitution of normal food for the diazepam-admixed food, various signs of diazepam withdrawal occurred 16-120 h later. These signs included vocalization, irritability, muscle rigidity, ear-twitching, Straub's tail, piloerection, fascicular twitch, tremor, convulsion, and death. The incidences of vocalization, ear-twitching, piloerection, and tremor in F344 were significantly higher than those in LEW rats. Furthermore, two of six F344 rats showed spontaneous convulsions and one rat died of convulsions. Overall withdrawal scores were significantly greater in F344 (16.0) than in LEW (6.3) rats. These results suggest that diazepam withdrawal severity is strongly influenced by genetic factors, and F344 rats are highly susceptible to dependence upon benzodiazepines.

Animals↗

Raised [3H]-5-HT release and 45Ca2+ uptake in diazepam withdrawal: inhibition by baclofen.

The effect of diazepam withdrawal (2 mg/kg/day) on release of [3H]-5-hydroxytryptamine(5-HT) and [14C]-GABA from rat cortical and hippocampal slices was studied. No changes in [14C]-GABA release (basal, K(+)-evoked, uptake) from slices of either region were observed. Similarly, all parameters of [3H]-5-HT release were unchanged in cortical slices. However, during diazepam withdrawal, depolarised [3H]-5-HT release from hippocampal slices was raised with no changes in basal release or uptake into the slices being found. This increase could be prevented by in vivo administration of 1 mg/kg baclofen--this dose having no significant effect on [3H]-5-HT release from hippocampal slices of control rats. To further investigate this effect, 45Ca2+ uptake into hippocampal synaptosomes was examined and found to be increased during withdrawal. This was blocked by in vitro addition of 10 microM (-)baclofen, which had no effect on 45Ca2+ uptake in controls. Inhibition of 45Ca2+ uptake by (-)baclofen was also enhanced in nonwithdrawn diazepam-treated rats, but not in rats treated acutely with diazepam. The results from both studies indicate that chronic diazepam treatment increases neuronal sensitivity to baclofen. These results are discussed with reference to the anxiogenic state during diazepam withdrawal and a recent report of reversal of this behaviour by baclofen.

Animals↗

Precipitated abstinence in the diazepam-dependent rat.

Physical dependence was produced in the rat by exposure to continuous release of diazepam from silastic capsule implants (recrystallized diazepam) or by dosing through a gastric fistula. The precipitated abstinence syndrome induced by the IV infusion of flumazenil was characterized by clonic and tonic-clonic seizures, retropulsion, digging, rearing, head, limb and body tremors, twitches and jerks of the body, and ear twitches. This abstinence syndrome differed both qualitatively and quantitatively from the milder syndrome induced in previous experiments by the intragastric administration of flumazenil in the diazepam-dependent gastric fistula rat. Capsule-implanted rats had free plasma and extraneuronal brain levels of diazepam, oxazepam, and nordiazepam in the 10(-3) and 10(-4) mg/ml range, and their brain: plasma ratios were not significantly different from 1. The diazepam capsules had a sustained release of over 28 days. These studies show that the capsule implantation technique is an efficacious way of maintaining plasma levels of diazepam and its metabolites, and producing a high level of physical dependence in the rat.

Animals↗

Effects of early protein malnutrition and environmental stimulation upon the reactivity to diazepam in two animal models of anxiety.

In order to investigate the effects of early protein malnutrition and environmental stimulation upon the response to the anxiolytic properties of diazepam, two animal models of anxiety (elevated plus-maze and light-dark transition tests) were used. Rats were malnourished by feeding their dams a 6% protein diet during the lactation period (0-21 days of age) while well-nourished controls received a 16% protein diet. From 21 to 70 days of age all rats received a balanced lab chow diet. Environmental stimulation consisted of 3-min daily handling from birth to 70 days of age. Additional stimulation was provided from 21 to 70 days of age by rearing the rats in an enriched living cage. Eight groups of rats were studied in a 2 (malnourished or well-nourished) x 2 (stimulated or nonstimulated) x 2 (diazepam or vehicle) design. At 70 days of age, independent groups of rats treated with diazepam (2.5 mg/kg, IP) or vehicle were submitted to testing in the elevated plus-maze or light-dark transition procedures. The results showed that both diazepam and environmental stimulation reduced anxiety in the elevated plus-maze; stimulation changed the anxiolytic response to diazepam and the two diet conditions altered differentially the response to both pharmacological and stimulation procedures. These results suggest that environmental stimulation can affect differentially the behavioral response of malnourished and well-nourished rats treated with diazepam.

Animals↗

Effects of triazolam and diazepam on learning and memory as assessed using a water maze.

One of the reported adverse side effects of the frequently prescribed benzodiazepines diazepam (Valium) and triazolam (Halcion) is an impairment of anterograde memory in humans. The experiments described in this article compared the effects of triazolam and diazepam on performance in a water maze task that is sensitive to drugs that affect learning and memory. The water maze utilized is a traditional type of maze with alleyways and door choices, unlike the Morris open water maze. Time required to find an out-of-the-water platform and errors committed during the swim are used as performance measures. Rats were tested on a previously learned maze configuration and on the acquisition of new maze configurations. Neither diazepam (0.25, 1.0, or 2.0 mg/kg) nor triazolam (0.05, 0.2, or 0.3 mg/kg) injected 30 min prior to testing on the previously learned maze affected swim time or errors committed. Administration of diazepam (0.5, 1.0, or 2.0 mg/kg, IP) prior to daily training on three different new maze configurations did not affect swim time, but did increase swim errors. Triazolam administered at 0.1, 0.2, or 0.3 mg/kg markedly impaired performance as assessed by either swim time or errors. There were no differences in performance of rats previously treated with triazolam, diazepam, or vehicle in learning another new maze after drug treatment was terminated. These data demonstrate that both diazepam and triazolam affect acquisition but not recall of maze configurations and support similar conclusions reached using other types of tasks in humans and animals.

Animals↗

Expression of Fos protein in various rat brain areas following acute nicotine and diazepam.

We studied the effects of an acute dose of (-)-nicotine (1 mg/kg) on Fos-like immunostaining (IS) in rat brain areas. Nicotine increased Fos IS significantly in the medial terminal nucleus of accessory optic tract (MT), and tended to increase it in the interpeduncular nucleus (i.p.), as well as in the stress-related areas, the paraventricular hypothalamic nucleus (PVN) and the supraoptic nucleus (SON). Previously nicotine was reported to increase Fos IS also in another stress-related area, the central nucleus of amygdala (ACe). This led us to study the interaction of nicotine with diazepam (10 mg/kg). Diazepam alone increased Fos IS in PVN and in SON as well as in ACe. In diazepam- and nicotine-treated rats Fos IS was increased in PVN and SON as well as in MT and i.p.. In MT and i.p. of diazepam and nicotine-treated rats Fos IS was similar to that induced by nicotine alone, and in PVN and SON of these rats Fos IS in ACe. Taken together, diazepam induced Fos IS in all stress-related areas studied (PVN, SON, ACe), but not in central visual structures, where nicotine induces Fos IS (MT, i.p.). No significant interactions on Fos expression were found between acute effects of diazepam and nicotine suggesting that these drugs activate different sets of neurons within the stress-related brain areas.

Amino Acid Sequence↗

Diazepam-stress interactions in the rat: effects on autoanalgesia and a plus-maze model of anxiety.

On six occasions spaced at least a week apart, two groups of rats were subjected to a variety of stressful conditions consisting of a restraint/bright light complex, either alone or in combination with a tail pinch, whole-body inversion, or partial immersion in cold water. One of these groups was injected with diazepam (2.0 mg/kg) 30 min prior to the stressors, while the other group experienced the drug in their home cages the following day. A third group also received the diazepam but was not exposed to the stressors. In three test sessions all animals were injected with either diazepam or saline and were then exposed to a novel stressor: a plus-maze used as a screening device for anxiolytic drugs. This was immediately followed by a tail-flick measure of analgesia. The longest tail-flick latencies, indicating stress-induced analgesia ("autoanalgesia"), were observed in the group that had not been exposed to stress prior to testing. The other two groups exhibited substantially shorter latencies but did not differ from one another, thus showing a "stress inoculation" effect that was uninfluenced by diazepam. In the plus-maze, diazepam tends to increase the amount of time rats will spend in the two exposed arms of the maze relative to the two enclosed arms. This effect was significantly attenuated in the group that had previously experienced the variety of stressors after a diazepam injection, suggesting a learned association between drug and stress that resulted in a diminution of the drug's anxiolytic property.

Animals↗

SCE in lymphocytes of patients treated with single, large doses of diazepam.

When using the SCE test for evaluation of exposure in vivo to potential mutagens/carcinogens, it is necessary to consider possible confounding factors. In studies of possible mutagenic effects of pharmacological treatment the effect of concomitant administration of other agents such as sedatives may have to be considered. In order to assess whether diazepam per se influences SCE we have examined SCE in peripheral lymphocytes in 34 persons before and after oral administration of a single large dose of diazepam. 18 men and 16 women undergoing minor surgery of the hand received diazepam 0.2 mg kg-1 body weight orally on the day of operation, and venous blood samples were drawn on the day before the operation and again 2-5 h after the administration of diazepam. Both within cigarette smokers and non-smokers there was no statistically significant change of SCE following diazepam. It was concluded that there was no indication, from the SCE test, of an immediate mutagenic effect of a single large dose of diazepam and that such medication is not a confounding factor in studies by the SCE test.

Adolescent↗

Effects of intravenous diazepam pretreatment on lactate-induced panic.

The psychological and physiological effects of acute low-potency benzodiazepine administration on lactate-induced panic were examined in 10 patients with panic disorder (PD). The patients, who had panicked during a standard sodium-lactate infusion, underwent a repeat infusion modified by pretreatment with intravenous diazepam (5 mg). Acute Panic Inventory (API) scores preceding the second lactate infusion, which were associated with diazepam pretreatment, were significantly reduced in compared with those measured before the first lactate infusion. However, the second visit "fear of doom" item of the API was significantly reduced relative to the same time point of the first visit 35 min before lactate infusion, when diazepam had not yet been administered. Thus, the reduction of prelactate anxiety preceding the second infusion appeared to reflect both pharmacological and nonpharmacological contributions. The diazepam pretreatment condition was associated with a significantly increased infusion duration and a significant attenuation of rate of API symptom increase in response to lactate. Despite significant attenuation of lactate infusion effects associated with the diazepam pretreatment condition, 7 of 10 patients experienced a second panic attack. This pilot study suggests that diazepam pretreatment is associated with a marked reduction of symptomatic response during a second lactate infusion, although the magnitude of attenuation observed was insufficient to block lactate-induced panic in a majority of lactate-vulnerable PD patients.

Adult↗

Modification of amygdaloid kindling by diazepam in juvenile rats.

The amygdaloid kindling phenomenon has been widely used to evaluate and screen potential anticonvulsant compounds in adult rats. In the current study, weanling rats (ages 23-25 days) were implanted chronically with amygdaloid electrodes. They were treated with dimethylsulfoxide (DMSO), 0.5 mg/kg diazepam or 1.0 mg/kg diazepam before twice daily kindling stimulations to determine the effect of diazepam on the acquisition of the kindled seizure. Additional juvenile rats implanted as weanlings and simulated twice daily without drug pretreatment until fully kindled were used to test for the acute anticonvulsant effects of diazepam (0.25-4.0 mg/kg). Diazepam was demonstrated to have anticonvulsant properties in juvenile rats by both prolonging the time to develop the fully kindled response during acquisition and by reducing the elicited seizure severity and the length of the afterdischarge in the fully kindled juvenile rats. Together, these data point to the extension of the anticonvulsant profile of diazepam to now include juvenile amygdaloid kindling in rats. They further point to the potential ability of screening proposed anticonvulsant drugs for their efficacy against amygdaloid kindling in immature rats.

Amygdala↗

Increase of tyrosine hydroxylase and its mRNA in the rat substantia nigra pars reticulata by diazepam and picrotoxin.

An involvement of GABAA receptors in the regulation of tyrosine hydroxylase (TH) gene expression in the substantia nigra pars reticulata (SNr) was investigated using immunohistochemistry (IMHC) and nonradioactive in situ hybridization histochemistry (ISH). The number of TH-positive cells was increased for both ISH and IMHC 8 h after a single administration of benzodiazepine diazepam, which facilitates GABAA-receptor-mediated transmission and reduces dopamine release in the substantia nigra (SN). Such increase in TH staining was suppressed when a dopamine D2 receptor agonist quinpirole was administered 10 min after diazepam. Co-administration of diazepam with a dopamine antagonist haloperidol did not further elevate, but rather, reduced haloperidol-induced increases in TH labeling. These results suggest that haloperidol and diazepam regulate TH gene expression in the SNr commonly by depressing dopaminergic transmission, and that diazepam activates TH expression in a group of SNr neurons which express this gene after haloperidol treatment. Moreover, a GABAA receptor antagonist, picrotoxin, activated TH gene expression in the SNr, and diazepam antagonized picrotoxin effects. Since picrotoxin increases neuronal activity, additional mechanisms will operate on TH gene expression. In conclusion, GABAergic substances will activate TH gene expression in SNr neurons (1) through decreasing spontaneous somato-dendritic dopamine release in the substantia nigra and/or (2) by increasing the activity of these neurons.

Animals↗

Comparison of withdrawal of buspirone and diazepam: a placebo controlled study.

In a 8-week double-blind placebo controlled study, 48 outpatients with generalized anxiety disorder were randomized to diazepam, buspirone, a non-benzodiazepine anxiolytic, or placebo. During the treatment phase of 4 weeks duration diazepam was found to be significantly better than placebo and buspirone. Following abrupt withdrawal by placebo substitution the diazepam group showed a gradual relapse maximal after two weeks while the buspirone and the placebo groups did not differ. There were more cases of rebound anxiety with diazepam as compared to buspirone or placebo. In addition, there were three early terminations related to rebound anxiety in the diazepam group while there were none in the placebo and buspirone groups. There were significantly more new symptoms in the diazepam group than in the placebo or buspirone group.

Adult↗

Effect of aging on the spatial learning deficit produced by diazepam in rats.

1. After pretraining in an undrugged state, young (6 months) and aged (18-24 months) rats were trained on a spatial learning-set task after receiving one of four doses of diazepam (1, 2, 3 or 5 mg/kg) or the drug vehicle. The effects of 5 mg/kg of diazepam were also assessed on the spatial learning-set task one full hour after injection (delay condition) as well as on the visible platform task. 2. During pretraining (undrugged), aged rats demonstrated a transient impairment on the visible platform task but subsequently did not differ significantly from young rats on the submerged platform task. On the spatial learning-set task, aged rats performed as well as young rats under control conditions and diazepam produced a comparable dose-dependent impairment of spatial learning. However, when the 1 hr delay was interposed between diazepam administration and maze testing, only aged rats exhibited a spatial learning impairment. Diazepam did not impair performance on the visible platform task in either young or aged rats. 3. These results indicate that although the amnesic effect of diazepam is not initially greater in aged rats, it persists for longer periods.

Aging↗